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An Insulin-to-Carbohydrate ratio (I:C) tells you how much rapid-acting insulin to give to cover the food your child eats. (Or, in other words, the I:C ratio specifies

For example, if your child’s I:C ratio is1:10, that means that1 unitof rapid-acting insulin is given for every10 grams of carbseaten; if the I:C ratio is1:15, 1 unit of insulin is given for every15 grams of carbseaten.

As an extension of this example, if your child uses a 1:15 ratio at breakfast you will give 1 unit of rapid for 15 grams of carb, 2 for 30, 3 for 45, 4 for 60, and so on (as well as 1.5 units for 22grams of carbs, and so on for other fractions of a unit).

Your child may use an Insulin-to-Carbohydrate ratio (I:C) if she is

You may need to adjust the ratio if there is a pattern of either high or low blood glucose following the use of the ratio.

For example: If you are using a ratio at breakfast you willexaminethe lunch blood glucose results to determine if the ratio isworking, or if it needs adjusting. If the ratio is working,a target blood glucose at breakfast will be followed by a target blood glucose at lunch.

If the lunch blood glucose consistently

For example, if the ratio is 1:15, you may lower the second number to, say, 1:12 to give more insulin. Before using the adjusted ratio to dose insulin, it’s always wise do a little “test” to make sure you have changed the ratio in the right direction: If your child was previously using a 1:15 ratio and ate 60 g carb, you would have given4 units. If you change the ratio to 1:12, you would now give 5 units for the same 60g carb (60 ÷ 12). Your changeresults in giving more insulinfor the meal, so was, therefore,correct.

(If your “test” shows that you will be giving less insulin with the adjusted ratio, and you know that your child should be getting more insulin to correct the pattern of high blood glucose, then you moved the second number of the ratio in the wrong direction.)

If the lunch blood glucose

For example, if the ratio is 1:15, you may raise the second number to, say, 1:20 to give more insulin. Before using the adjusted ratio to dose insulin, again it’s wise do a little “test” to make sure you have changed the ratio in the right direction: If your child was using a 1:15 ratio and ate 60 g carb you would have given 4 units. If you now change the ratio to 1:20 you would give 3 units for the same 60g carb (60 ÷ 20). Your changeresults in giving less insulinfor the meal, so was, therefore,correct.

To calculate the actual amount of insulin that should be delivered in a carb bolus, you divide the grams of carbs in the meal/snack by the second number in the ratio.

For example, if your child is about to eat a snack containing 30 grams of carbs, and his I:C ratio is 1:10, you divide 30 by 10, arriving at 3 as a result. This means your child should receive 3.0 units of insulin for that snack.

Note that higher numbers in the ratio indicate less insulin (for a constant amount of carbs). That is, for a snack containing 30 grams of carbs, an I:C ratio of 1:10 would mean your child receives 3.0U of insulin, as in the preceding example. However, an I:C ratio of 1:15 would mean your child receives 30 divided by 15 = 2.0U of insulin. This is an important point for adjusting I:C ratios: if your child’s blood glucose is consistently below-target at a certain time of day, and you decide that the solution is to give her less bolus insulin for the preceding meal/snack, you would increase the second number in the I:C ratio; conversely, if your child’s blood glucose is consistently above-target at a certain time of day, and you decide that the solution is to give her more bolus insulin for the preceding meal/snack, you would decrease the second number in the I:C ratio.

For more information on insulin adjustment, see the articles under BG Management on this website.

For guidance in working out these adjustments, please consult with your child’s diabetes health care team.

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